It is known to mount a subframe on a vehicle body frame via mount bushes having a relatively high compliance and pivotably attach inner ends of suspension arms to the subframe via mount bushes having a relatively low compliance to the end of preventing the vibrations transmitted from the tires to the suspension arms from reaching the vehicle body, and to ensure a high rigidity against changes in wheel alignment.
Normally, such a subframe comprises a pair of spaced apart parallel longitudinal members, and a pair of parallel lateral members connecting the front and rear ends of the longitudinal members one another, and thus has a rectangular annular shape as seen in plan view. Therefore, it is advantageous to place a fuel tank inside the space defined by the subframe members to protect the fuel tank from possible damages.
When a fuel tank is placed inside the space defined by the subframe members, the sloshing movement of the fuel inside the fuel tank tends to apply a twisting force to the subframe. The subframe members normally have closed cross sections to be resistant against such twisting deformation, and the subframe as a whole is relatively rigid against twisting deformation. Therefore, the sloshing movement of fuel inside the fuel tank tends to cause undesirable vibrations of the vehicle body which could be noticed by the vehicle occupants.
An automotive fuel tank is typically made of a pair of halves each formed into the shape of a flanged bowl by stamping sheet metal, and welding them together along the flanges extending along the outer rims of the two halves. Therefore, when such a fuel tank is placed inside the space defined by the subframe members, the interference between the flange and the subframe members limits the effective lateral dimension or the capacity of the fuel tank.